Handling of inspired vaporized ethanol in the airways and lungs (with comments on forensic aspects)

Collections of expired air and chemical determinations of ethanol concentrations in inspired and expired air showed that during prolonged inspiration of ethanol (vapour)-containing air about 55% was absorbed by adult human subjects. The fractional absorption was not detectably affected by variations in tidal volume (0.7-2.1 liters), nor was it significantly reduced in experiments where, due to preceding oral intake, the ethanol concentration of systemic blood was up to 50 times higher than that of inspired air. In these experiments the difference between the rates of change in blood alcohol concentration (beta 60) during and before ethanol inhalation agreed well with values calculated from measured respiratory absorptions. Mass spectrometric recordings of ethanol concentration in expired air vs. expired volume, taken in a state of steady uptake, also gave absorption fractions of about 0.55, and showed that the concentration in end-expiratory air did not fall below some 30% of that of the inspired air. These and other findings show that a large part of ethanol being inspired is deposited in the airway linings to be released again to ethanol-free alveolar air expired through the airways. It is concluded that inspired ethanol deserves consideration as a source of elevations of blood alcohol concentrations.